LITTLE ROCK (AP) - The operator of a Springdale turkey plant responsible for a massive ground turkey recall was searching for answers Thursday to what caused a salmonella outbreak that's been linked to one death and at least 77 illnesses.

Officials at the meat giant Cargill were trying to determine how a strain of salmonella got into ground turkey shipped from northwest Arkansas, said company spokesman Mark Klein.

The Agriculture Department asked the Minnesota-based company to recall 36 million pounds of ground turkey sent to grocery stores nationwide over a six-month period.

"We're looking all the way from the plant back to the birds on the farm," Klein said.

Arkansas is one of the country's biggest producers of turkey, chickens and eggs. It produced the third-most turkey of any state in 2009, according to The Poultry Federation.

One death in California and several illnesses nationwide have been linked to the outbreak. No illnesses were reported in Arkansas.

"It's hard to track down sporadic cases," said John Marcy, an extension food scientist at the University of Arkansas' Center for Excellence for Poultry Science.

Marcy said no inspection process could completely eliminate salmonella, which occurs naturally in turkey and other animal products.

"As a consumer, you have to assume that any raw food of animal origin has salmonella and handle it accordingly," he said.

Consumers are generally warned to cook ground turkey to at least 165 degrees and to handle it properly. They also have been asked to check their freezers for contaminated products because frozen turkey has a long shelf life.

Cargill's 1,200-employee plant in Springdale has stopped making ground turkey during its investigation, but the plant continues to produce other turkey products.

Klein said he hoped the company's efforts to fix the problem would restore confidence going forward.

"We don't know what will happen," Klein said. "We will have to rely on what we've done in the past, and we have done a number of good things in the past, and then how we move forward. We'll be judged on that, which is appropriate."